Plastic composition and the method of compounding the same



Patented Sept. 14, 1937 UNITED. STATES PLASTIC COMPOSITION. AND "EHE'METHOD F COMPOUNDING THE SAME Arthur F. Rowe, Lansing, Mich.

N0 Drawing. Application May 6, 1936,--

Serial No. 78,072

continuation-in-part of an earlier application.

Serial No. 472,492 filed August 1, 1930.

The principal object of this invention is to provide a plastic composition which dries upon ex-,

posure to the air without shrinking and which when dried is hard and tough but not brittle. This object is attained in part by combining various ingredients in the proportions specified hereinafter and more particularly by the method of compounding the same.

Prior to the present invention there were various plastic compositions for use in filling wood crevices and similar purposes. All of these plastic compositions of the prior art have a tend ency either to shrink and become brittle upon exposure to the air or are soluble in various fluids such as water, gasoline and lacquer. The present invention provides a plastic composition which hardens upon drying but does not shrink and which is insoluble in the various fluids mentioned above as well as most others. Accordingly, the plastic composition compounded as hereinafter described is especially suitable for use in filling screw holes, or the like, in the bottom of boats or other articles normally immersed in water or other fluids. The present plastic composition is also especially adapted for use-in' filling crevices in furniture and similar articles where lacquer or similar finishing materials are used as a coating over the plastic. composition.

In the preferred form of the invention a small quantity of bleached litharge is added to a quantity of nitro-cellulose solvent. After being introduced into the nitro-cellulose solvent the litharge is worked in any suitable manner to break the same up into finely divided particles andto thoroughly mix the same with the solvent. Preferably as much litharge is added to the nitrocellulose solution as the solution will hold in suspension. It should be here understood that, while it is believed that the litharge is merely sus: pended in the form of fine particles in the nitrocellulose solution, it may be that the same is dissolved or that a chemical reaction occurs between the nitro-cellulo-se solution and the litharge. Regardless of the nature of the action which occurs it is essential that the litharge be thoroughly mixed with the nitro-cellulose solution until the resulting product is homogeneous throughout.

The nitro-cellulose solvent may consist of any of the conventional solvents of this character. A satisfactory solvent comprises thirty parts of butyl acetate, sixty parts of toluol and ten parts of butyl alcohol. This solution is what may be termed a slow solvent. A solution consisting of fifty partsof toluol, twenty-five parts of thymal alcohol, twelve and a half parts ethyl acetate and. twelve and a halfn'par tsbenzol constituteswhat may. be called a fast: solvent; The nature of the use to which the plastic compositionv is to. be sub-. jected will determine. the character of the solvent which is .to be used.

After the litharge has been .addedto the nitro-.

cellulose solvent as described above, the product thusiormed is added to a nitro-cellulose solution. The quantity of.'the.nitro-cellulose solution is such that the mixture of litharge and nitrocellulose solvent can be thoroughly and homogeneously admixed therewith before the result.

ing. mass thickens to' such an extent as to prevent further admixture Thesolvent containing the litharge. and the nitro cellulose solution is stirred or mixed continuouslyuntil the solution substantially transparent paint which is waterproof. and whichis insoluble in water, alcohol, gasoline, andfth'e like.

While it isjprefer red to form a premixture of litharge and nitro-cellulose solvent as described herein andthereafter adda Intro-cellulose solution thereto, if desired, the lithar'ge may be addedj to a relativelylarge quantity of nitrocellulose solvent in which case any form of nitrocellulose (not in solution) and a suitable ester gum may then beadded to the mixture. of nitrocellulose.solventandthe litharge. Likewise, the litharge may be.added...directly to anadequate quantity of .-nitro=ce1lulose. solution without the preliminary formationof. themixtureof litharge andnitro-cellulose solvent providing the litharge isjhomogeneouslyj. mixed, with the nitro-cellulose solution. J'I t,has been found; however, that the nitro cellulose'solutio-n has a, tendency to thicken.

so rapidly upon'thef introduction of litharge directly' thereinto that it. is substantially. impossible to "stributethelithargefhomogeneously.through- H thesame' without-first forming a preliminary mixture, of nitio-celliflosej solvent and litharg. In anyjcasait' is. essential that the litharge be so thoroughly mixed with the nitro cellulose solution.

that itjis homogeneously distributed. throughout t t: solution. 1 I f Whereit-i s desired to give the plastic composition a; distinctiveeolOr thenecessary quantityofsuitable pigments may be added either to thernix ture of lithar'ge and nitro-cellulose solvent or to the nitro-cellulose solution at the time the mixture of litharge and nitro-cellulose solvent is added thereto.

After the litharg-e has been mixed with the nitro-cellulose solution to form a homogeneous viscous mass, the same is introduced into a receptacle containing a homogeneous mixture of various filler materials. These fillers which have been previously thoroughly mixed preferably include finely divided wood flour, silica, and whiting. The proportion of these fillers will vary depending upon the characteristics desired in the resulting product. Any other suitable fillers in varying quantities may be used although it is preferred in any case that some form of fibrous material be included in the fillers as such material forms the best type of binder.

The nitro-cellulose solution containing the litharge and the fillers is thoroughly kneaded until the resulting product is of a uniform plastic consistency. The quantity and proportions of fillers used will depend upon the character of plastic composition desired. For a composition which will be suitable as a surface glaze a relatively small quantity of filler will be used. Where the resulting product is to be used as a filler for screw holes, or the like, a relatively greater quantity of filler will be used.

The nitro-cellulose solution used in preparing the present plastic composition preferably consists of two pounds of nitro-cellulose and one pound of ester gum dissolved in one gallon of nitro-cellulose solvent. The solvent preferably consists, as mentioned hereinbefore, of thirty parts of butyl acetate, sixty parts of toluol and ten parts of butyl alcohol.

The fillers are preferably mixed in the following approximate proportions:

, Percent Whiting 65 to 75 Silex 10 to 15 Wood flour 10 to 25 Nitro-cellulose solution 2 quarts Litharge 3 ounces Whiting 8 pounds Silex 1 pounds Wood flour 1 to 3 pounds Instead of adding the fillers to the homogeneous mixture of litharge and nitro-cellulose solution as just described, the mixture may be diluted with additional nitro-cellulose solvent to produce a liquid paint or surfacer having all the desirable characteristics of the plastic composition. That is to say, the surfacer will dry quickly upon exposure to air and when dried is hard and tough but not brittle. It will not chip. Likewise, when dry the surfacer thus formed is insoluble in such fluids as water, gasoline, lacquer and the like.

Best results are obtained in producing the surfacer or paint from the plastic composition base by diluting the same so that it contains not less than twenty and not more than fifty percent of solids. The amount of litharge used will depend upon the percentage of solids. The proportion of litharge will vary from approximately onesixteenth ounce to a gallon of nitro-cellulose solution containing twenty percent solids to one-quarter ounce of litharge to a gallon of solution containing fifty percent of solids. In any event, the litharge must be homogeneously mixed with a small quantity of solvent before-being added to the nitro-cellulose solution.

The base for the plastic composition may be originally prepared of a consistency suitable for use as a paint or surfacer.

To produce the plastic composition, it is then only necessary to increase the percentage of solids in the base and add the fillers in the proportions previously recited.

A base suitable for use as a paint or surfacer is prepared as follows: approximately one-sixteenth ounce of bleached litharge is added to a small quantity of nitro-cellulose solvent and homogeneously mixed therewith. The amount of solvent that is used is immaterial, the only requisite being that sufiicient solvent is used to permit a complete and homogeneous dissolution or suspension, as the case may be, of the litharge in the solvent. For the purpose of this preliminary mixture any of the constituent parts of the solvent may be used in lieu of the solvent if desired.

The homogeneous mixture of litharge and solvent prepared as just described is then added to and thoroughly mixed with approximatelyv one gallon of nitro-cellulose solution containing approximately twenty percent of solids. The product thus formed is of suitable viscosity to permit application by means of brushes or sprays such as those conventionally used in the application of paints and lacquers.

While only certain typical proportions of the ingredients required have been set forth herein it should be understood that these may be varied within relatively wide limits so long as the litharge is ultimately thoroughly and homogeneously mixed with the nitro-cellulose solution. The scope of the invention is indicated in the appended claims.

I claim:

1. The method of compounding a base for plastic compositions suitable for use as a paint or surfacer which comprises forming a preliminary homogeneous mixture of litharge and nitro-cellulose solvent and thereafter introducing into and thoroughly mixing with such preliminary mixture a quantity of nitro-cellulose solution, the proportions of the litharge to the nitrocellulose solution being between approximately one-sixteenth and one-quarter ounce of litharge to approximately one gallon of nitro-cellulose solution of a character containing between twenty and fifty percent of solids.

2. A base for a plastic composition suitable for use as a paint or surfacer comprising a homogeneous mixture of litharge and nitro-cellulose solution combined in the proportions of between one-sixteenth and one-quarter ounce of litharge to one gallon of nitro-cellulose solution of a consistency varying from twenty to fifty percent of solids.

ARTHUR F. ROWE. 

